1. Field of the Invention
The present invention relates to a variable compression ratio (VCR) apparatus, and more particularly, to a VCR apparatus having dual eccentric links and dual swing links.
2. Description of Related Art
In general, the thermal efficiency of a heat engine increases when a compression ratio is high. In the case of a spark ignition engine, the thermal efficiency thereof increases when ignition timing is advanced to a predetermined level.
In the spark ignition engine, however, when the ignition timing is advanced at a high compression ratio, abnormal combustion may occur to cause engine damage. Therefore, there is a limit in advancing the ignition timing. Thus, the spark ignition engine should endure an output reduction.
A VCR apparatus serves to change the compression ratio of gas mixture depending on an operation state of an engine.
The VCR apparatus improves fuel efficiency by increasing the compression ratio of the gas mixture in a low-load condition of the engine. Further, the VCR apparatus prevents the occurrence of knocking and improves engine power by reducing the compression ratio of the gas mixture in a high-load condition of the engine.
U.S. Pat. No. 6,581,552 has disclosed a VCR apparatus according to the related art. The VCR apparatus includes a connecting rod having one end connected to a piston forming a combustion chamber and the other end connected to a crank shaft. The one end of the connecting rod is coupled to an eccentric ring. The eccentric ring is connected to one end of an eccentric swing member. The other end of the eccentric swing member is connected to a slide through a coupling. The slide is connected to a driving device so as to be moved by the driving device.
The slide is moved by the operation of the driving device, and the motion of the slide is transmitted to the eccentric swing member through the coupling so as to rotate the eccentric swing member. The rotation of the eccentric swing member varies the top dead center of the piston through the connecting rod, thereby changing the compression ratio of the combustion chamber formed by the piston.
In the VCR apparatus according to the related art, the structural stiffness and stable operation of the eccentric swing member are required, and the structure of the eccentric swing member needs to be simplified.
The information disclosed in this Background of the Invention section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.